The present invention relates to high temperature separation of fluids using a ceramic membrane device and a method for separating fluids at high temperatures using a ceramic membrane device.
Ceramic membranes have been widely used in liquid phase separations in pharmaceutical, food, beverage and other industries. Recently, they have also been tested for gas separations (Wu, J. C. S., et al, "High Temperature Separation of Binary Gas Mixtures Using Microporous Ceramic Membranes", J. Membrane Science, 77, 85 (1993)) and catalytic reactions (G. Saracco & V. Specchia, "Catalytic Inorganic Membrane Reactors, Present Experience and Future Opportunities", Cataly. Review - Sci. Eng., 36, 305 (1994)). Ceramic membranes have the advantage of improved thermal and chemical stability over polymeric membranes commonly used in industrial separations.
The use of ceramic membrane tubes in the prior applications is set forth, for example, in F. M. Velterop et al, "Development of a High Temperature Resistant Module for Ceramic Membranes", Key Engineering Materials, 61 & 62, 391 (1991), wherein there is disclosed processes such as solid/liquid separation, gas separation and membrane reactor applications. It is noted that ceramic membranes do not find use at high temperatures because of the difficulty in sealing and securing the ceramic membranes in high temperature modules made of different materials, for instance, metals. For purposes of sealing, Veltrop suggests a metallic bellows between the ceramic membrane and the housing. This permits a multiple layer brazing technique for joining (see G. Saracco et al, "Catalytic Inorganic Membrane Reactors, Present Experience and Future Opportunities", Cataly, Review - Sci. Eng., 36, 305 (1994). However, this approach is very costly and complicated.
Velterop U.S. Pat. No. 5,139,191 discloses a method of connecting a ceramic material to another material. According to the method, porous material is used that, prior to making a connection is gradually compacted from the contact surface with the greatest density at the contact surface, wherein on the contact surface of the porous material a mixture of titanium hydride (TiH.sub.2) and quartz flour (SiO.sub.2) is applied. Then the so treated porous ceramic material is heated to 1200.degree.-1800.degree. C. during 1-40 hours. Finally the so compacted porous ceramic material, in a manner known per se, is connected to the other material.
Goldsmith U.S. Pat. No. 4,781,831 discloses a cross-flow filtration device which separates a feed stock into filtrate and retentate, including a structure of porous material which defines a plurality of passageways extending longitudinally from the feed end of the structure to a retentate end, and a number of filtrate conduits within the structure for carrying filtrate from within the structure toward a filtrate collection zone.
Jordan U.S. Pat. No. 3,664,507 discloses filter robes in a resilient holder wherein a filter unit is used for the fine filtration of various fluids with the filter element comprising a plurality of elongated, hollow rods made of a rigid porous material that are individually held in position by a resilient holder.
Sauder U.S. Pat. No. 4,177,036 discloses a high temperature industrial furnace comprising a clean interior face of a metal furnace casing, a corrosion inhibitor/adhesive, and a ceramic fiber insulation module attached to the casing with the adhesive to provide an elastic or flexible bond between the casing and the insulating material. The corrosion inhibitor/adhesive may be applied over a relatively large surface area of the casing to provide a vapor impervious membrane. A silicone compound is a preferred corrosion inhibitor/adhesive material.
However, it will be seen from the above that there is still a great need for a ceramic membrane device that may be employed economically for high temperature separation of gases or liquids, for example.